IUBMB Enzyme Nomenclature


Accepted name: thyroxine 5'-deiodinase

Reaction: 3,3',5-triiodo-L-thyronine + iodide + acceptor + H+ = L-thyroxine + reduced acceptor

Glossary: 3,3',5-triiodo-L-thyronine = O-(4-hydroxy-3-iodophenyl)-3,5-diiodo-L-tyrosine
L-thyroxine = O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-L-tyrosine

Other name(s): diiodothyronine 5'-deiodinase [ambiguous]; iodothyronine 5'-deiodinase; iodothyronine outer ring monodeiodinase; type I iodothyronine deiodinase; type II iodothyronine deiodinase; thyroxine 5-deiodinase [misleading]; L-thyroxine iodohydrolase (reducing)

Systematic name: 3,3',5-triiodo-L-thyronine,iodide:acceptor oxidoreductase (iodinating)

Comments: The enzyme activity has only been demonstrated in the direction of 5'-deiodination, which renders the thyroid hormone more active. The enzyme consists of type I and type II enzymes, both containing selenocysteine, but with different kinetics. For the type I enzyme the first reaction is a reductive deiodination converting the -Se-H group of the enzyme into an -Se-I group; the reductant then reconverts this into -Se-H, releasing iodide.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Chopra, I.J. and Teco, G.N.C. Characteristics of inner ring (3 or 5) monodeiodination of 3,5-diiodothyronine in rat liver: evidence suggesting marked similarities of inner and outer ring deiodinases for iodothyronines. Endocrinology 110 (1982) 89-97. [PMID: 7053997]

2. Goswani, A., Leonard, J.L. and Rosenberg, I.N. Inhibition by coumadin anticoagulants of enzymatic outer ring monodeiodination of iodothyronines. Biochem. Biophys. Res. Commun. 104 (1982) 1231-1238. [PMID: 6176242]

3. Smallridge, R.C., Burman, K.D., Ward, K.E., Wartofsky, L., Dimond, R.C., Wright, F.D. and Lathan, K.R. 3',5'-Diiodothyronine to 3'-monoiodothyronine conversion in the fed and fasted rat: enzyme characteristics and evidence for two distinct 5'-deiodinases. Endocrinology 108 (1981) 2336-2345. [PMID: 7227308]

4. Körhle, J. Iodothyronine deiodinases. Methods Enzymol. 347 (2002) 125-167. [PMID: 11898402]

[EC created 1984 as EC, transferred 2003 to EC, transferred 2015 to EC]

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